Both digital and analog adaptive line enhancers act as narrowband filters to enhance the narrowband frequency components present in a broadband noise field. Adaptive line enhancers are constructed so that they automatically adjust to variations in the input signal in order to provide a least mean square (LMS) approximation of a WienerHopf filter. This device uses a number of stored weight values which are continuously adjusted so that the device automatically filters out the components of the signal which are not correlated in time in order to pass correlated stable spectral lines.
The McCool et al U.S. Pat. No. 4,238,746 issued Dec. 9, 1980 entitled "Adaptive Line Enhancer," the McCool et al U.S. Pat. No. 4,243,935 issued Jan. 6, 1981 entitled "Adaptive Detector" and the article entitled "The Time-Sequenced Adaptive Filter" by Ferrara, Jr. and Widro which was published 1981 in the IEEE Transactions on Circuits and Systems, Vol. CAS-28 (1981) June N 6, New York USA show prior art devices and/or provide discussions of the theoretical basis of the adaptive line enhancer.